Cane Toad Bufo Marinus Research Articles

Microvascular anatomy and physiology laboratory class using the Australian cane toad

The microvasculature is a key part of the cardiovascular system and teaching microvascular structure and function is a key part of any cardiovascular science course. The Australian cane toad Bufo marinus / Rhinella marina is an economical and widely available species within Australia which can be used to demonstrate basic principles of blood flow and microvascular anatomy and physiology in an in vivo setting.In the laboratory class, cane toads of either gender (approx. 120 g) are anesthetized by immersion in 0.3 % ethyl 3‐aminobenzoate methanesulfonate (MS‐222) for 15 min and for the duration of the class (about 2 hr) swabs soaked in MS‐222 are placed on the skin. Level of anaesthesia is regularly assessed by the corneal reflex. At the end of the class toads are euthanized by cardiac removal (UNSW ACEC approval #19/67B). The surgical procedure involves a small incision in the upper abdomen, through which a lung, the bladder and the mesentery may be exteriorized and the microvasculature examined under a microscope equipped with a camera for video streaming to high definition monitors.The class is designed to demonstrate principles delivered in lectures and allow students to integrate knowledge of these principles into microvascular homeostasis and adaptation to interventions. Microvascular features which can be clearly demonstrated include microvascular anatomy and structural adaptations in different tissues, including the lung (pulmonary microcirculation), urinary bladder and mesentery. Observable physiological phenomena include blood flow velocity and its’ effect blood cell behaviour, axial streaming, plasma skimming, leukocyte rolling and adhesion, vasoconstriction and the response of the mesenteric microvasculature to haemorrhage.Student learning is assessed through pre‐ and post‐class exercises completed on‐line. The pre‐class exercise includes demonstrative videos and a brief quiz. This is intended to ensure students have read and understood the laboratory class notes, along with some basic vascular science, prior to the class, avoiding time‐wasting. The post‐class exercise includes video material recorded during the class accompanied by a quiz aimed at testing the students’ understanding of the observations made; for example, the physiological advantage of unique microvascular anatomy in certain tissues, or the mechanism underlying capillary swelling and hemodilution during haemorrhage. The videos can be edited into a package and used to deliver the class in an on‐line format if required. Thus, the cane toad preparation allows key aspects of microvascular anatomy, physiology, pharmacology and rheology to be demonstrated and taught in a clear and compelling fashion.

Frogs fine-tune springy muscle and tendon for leaps

Long before the advent of gunpowder, humans had harnessed the power of catapults in warfare to destructive effect. Yet, biology had already beaten us to capitalising on the power of springs. ‘Fast and powerful movements like the jump of the flea or the strike of a mantis shrimp smasher are possible because they use elastic energy storage mechanisms’, says Elizabeth Mendoza from the University of California, Irvine, USA. Even soft-bodied frogs get in on the action, storing energy in the plantaris longus muscle–tendon unit – linking the back of the knee to the heel – ready for release in powerful leaps. Yet in 2011, when Tom Roberts, Emily Abbott and Manny Azizi investigated the source of energy powering the jumps of three frog and toad species, they were surprised that the animals’ explosive launches were driven by plantaris longus muscle contractions of about the same power (∼300 W kg−1), even though Cuban tree frogs (Osteopilus septentrionalis) leapt with a take-off power of ∼1100 W kg−1 while cane toads (Bufo marinus) achieved take-offs with a power of ∼200 W kg−1. Realising that the animals must be fine-tuning the energy storage capacity of the springy plantaris longus muscle–tendon unit, resulting in vastly different propulsion, Mendoza and Azizi scrutinised the legs of cane toads, Cuban tree frogs and bullfrogs (Rana catesbeiana) to determine how they differed. ‘All of our animals came from the pet trade’, says Mendoza, who collected samples of the animals’ plantaris longus muscle–tendon units to measure the amount of force exerted by the muscles as they contracted. ‘There are many challenges with this technique’, says Mendoza, such as keeping the muscle alive, making sure the nerve branch was not crushed or pulled too hard, and keeping the muscle–tendon unit securely in place in the force measuring rig. Then, she and Azizi investigated the structure of the frogs’ plantaris longus muscles, cutting the muscle open to reveal the featherlike arrangement of the fibres within to measure their stacking angle relative to the direction in which the muscle pulls (the pennation angle). Finally, the duo calculated how much work the muscle did during a contraction and the overall stiffness of the muscle–tendon unit to find out how much energy it could store.After months of painstaking analysis, it was clear that the plantaris longus muscle–tendon unit of the Cuban tree frog stood out from the crowd. ‘It was modified for increased elastic energy storage’, says Mendoza, explaining that the structure is stiffer than that of the cane toad and bullfrog muscle–tendon unit, allowing the Cuban tree frogs to store more elastic energy to power their mighty leaps. In addition, when Mendoza and Azizi measured the force generated by the tree frog's muscle (∼30 N g−1), it was almost double that produced by the cane toad and bullfrog (∼17 N g−1).But how was the tree frog's muscle able to generate so much force when it was so much smaller (∼0.3 g) than the bullfrog and cane toad's muscles (∼1.3 and ∼1 g, respectively)? Scrutinising the muscle structures, the duo realised that the muscle fibres in the Cuban tree frog plantaris longus were stacked at a much steeper angle (∼25 deg compared with the cane toad and bullfrog's 20 deg pennation angle), allowing the tree frogs to pack more fibres into the muscle to generate more force.‘A tuned increase in muscle force and elastic structure stiffness increases elastic energy storage in Cuban tree frogs’, says Mendoza, and Azizi adds, ‘In terms of jump distance, Cuban tree frogs are the best, followed by bullfrogs and then cane toads’. So, the Cuban tree frog's springier legs tie in nicely with their exceptional vaulting abilities.

Mechanisms of Convergent Egg Provisioning in Poison Frogs.

Parental provisioning of offspring with physiological products (nursing) occurs in many animals, yet little is known about the neuroendocrine basis of nursing in non-mammalian species. Within amphibians, maternal provisioning has evolved multiple times, with mothers of some species feeding unfertilized eggs to their developing offspring until tadpoles complete metamorphosis [1-3]. We conducted field studies in Ecuador and Madagascar to ask whether convergence at the behavioral level provides similar benefits to offspring and relies on shared neural mechanisms in dendrobatid and mantellid poison frogs. At an ecological level, we found that nursing allows poison frogs to provide chemical defenses to their tadpoles in both species. At the neural level, nursing was associated with increased activity in the lateral septum and preoptic area, demonstrating recruitment of shared brain regions in the convergent evolution of nursing within frogs and across vertebrates [4]. In contrast, only mantellids showed increased oxytocin neuron activity akin to that in nursing mammals [5], suggesting evolutionary versatility in molecular mechanisms. Our findings demonstrate that maternal provisioning provides similar potential benefits to offspring and relies on similar brain regions in poison frog species with convergently evolved toxicity and maternal care. VIDEO ABSTRACT.

Survey of Ranavirus and Batrachochytrium dendrobatidis in Introduced Frogs in Hawaii, USA

Ranaviruses and the fungus Batrachochytrium dendrobatidis are globally important agents of emerging infectious amphibian diseases. Amphibians on Oahu, the Hawaiian Island with the greatest potential for disease introduction through the movement of goods and people, have never been surveyed for ranaviruses or B. dendrobatidis. We surveyed all five species of frogs on Oahu, Hawaii, US for these pathogens. Of 325 individuals sampled from six sites, none were positive for ranavirus. However, we found B. dendrobatidis in a total of four individuals of three species, the cane toad (Bufo marinus), the American bullfrog (Rana catesbeiana), and the greenhouse frog (Eleutherodactylus planirostris), but not in the green and black poison dart frog (Dendrobates auratus) or the Japanese wrinkled frog (Rana rugosa). The apparent lack of ranavirus and low prevalence of B. dendrobatidis are noteworthy given how widespread these pathogens are in terms of both global distribution and host range. Surveillance should continue to document any changes in B. dendrobatidis prevalence or the arrival of ranaviruses in Hawaii.

No signs of Na+/K+‐ATPase adaptations to an invasive exotic toxic prey in native squamate predators

AbstractInvasions by exotic toxic prey, like the release of the South American cane toad (Bufo (Rhinella) marinus) to the toad‐free Australian continent in 1935, have been shown to result in massive declines in native predator numbers. Due to minor nucleotide mutations of the Na+/K+‐ATPase gene most Australian squamate predators are highly susceptible to cane toad toxin. However, in spite of this, predators like yellow‐spotted goannas (Varanus panoptes) and red‐bellied black snakes (Pseudechis porhyriacus) still persist in parts of Queensland where they, in some areas, have co‐existed with cane toads for more than 70 years. Here, we show that the amino acids of the Na+/K+‐ATPase enzyme in the two species do not provide toad toxin resistance, and hence the two Queensland predators are still highly susceptible to cane toad toxin. Both yellow‐spotted goannas and lace monitors (Varanus varius) have, however, been recorded avoiding feeding on cane toads in areas where they co‐exist with this toxic amphibian. Moreover, both varanids have also been shown to learn to avoid feeding on toads when first subjected to conditioned taste aversion. Such behavioural shifts may therefore explain why yellow‐spotted goannas and red‐bellied black snakes still exist in cane toad infested areas of Queensland. The process appears, however, to be unable to rapidly restore varanid populations to pre‐toad population numbers as even after 10 years of co‐existence with cane toads in the Northern Territory, we see no signs of an increase in yellow‐spotted goanna numbers.

Aqueous and Ethanol Extracts of Australian Cane Toad Skins Suppress Pro‐Inflammatory Cytokine Secretion in U937 Cells via NF‐κB Signaling Pathway

Toad skin extracts, such as aqueous extracts (AE) of Chinese toad skins, have demonstrated therapeutic benefits for a range of diseases including pain, inflammation, swelling, heart failure, and various types of cancers. In this study, we investigated the anti-inflammatory potential of an AE (0.1-10 μg/mL) and a 60% ethanol extract (EE; 0.1-10 μg/mL) from Australian cane toad (Bufo marinus) skins and the known bioactive compound, bufotenine (BT; 0.1-10 nM). The assay employed a model of the human monocyte cell line U937 stimulated with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA) for the release of tumor necrosis factor (TNF)-α and interleukin (IL)-6. We demonstrated that AE, EE, and BT significantly inhibited the release and expression of TNF-α and IL-6 in a dose-dependent manner when the cells were pre-treated at non-cytotoxic concentrations. Further investigation revealed that the inhibition of TNF-α and IL-6 release and expression was associated with the suppression of nuclear factor (NF)-kappa (κ)B activation. These results indicate that AE, EE, and BT are strong inflammation inhibitors, thus have the potential for further development as anti-inflammatory therapeutic agents from a natural source regarded as a feral pest in Australia. J. Cell. Biochem. 117: 2769-2780, 2016. © 2016 Wiley Periodicals, Inc.

Predator interference effects on biological control: The “paradox” of the generalist predator revisited

An interesting conundrum in biological control questions the efficiency of generalist predators as biological control agents. Theory suggests, generalist predators are poor agents for biological control, primarily due to mutual interference. However field evidence shows they are actually quite effective in regulating pest densities. In this work we provide a plausible answer to this paradox. We analyze a three species model, where a generalist top predator is introduced into an ecosystem as a biological control, to check the population of a middle predator, that in turn is depredating on a prey species. We show that the inclusion of predator interference alone, can cause the solution of the top predator equation to blow-up in finite time, while there is global existence in the no interference case. This result shows that interference could actually cause a population explosion of the top predator, enabling it to control the target species, thus corroborating recent field evidence. Our results might also partially explain the population explosion of certain species, introduced originally for biological control purposes, such as the cane toad (Bufo marinus) in Australia, which now functions as a generalist top predator. We also show both Turing instability and spatio-temporal chaos in the model. Lastly we investigate time delay effects.

Nerve–muscle activation by rotating permanent magnet configurations

The standard method of magnetic nerve activation using pulses of high current in coils has drawbacks of high cost, high electrical power (of order 1 kW), and limited repetition rate without liquid cooling. Here we report a new technique for nerve activation using high speed rotation of permanent magnet configurations, generating a sustained sinusoidal electric field using very low power (of order 10 W). A high ratio of the electric field gradient divided by frequency is shown to be the key indicator for nerve activation at high frequencies. Activation of the cane toad sciatic nerve and attached gastrocnemius muscle was observed at frequencies as low as 180 Hz for activation of the muscle directly and 230 Hz for curved nerves, but probably not in straight sections of nerve. These results, employing the first prototype device, suggest the opportunity for a new class of small low-cost magnetic nerve and/or muscle stimulators. Conventional pulsed current systems for magnetic neurostimulation are large and expensive and have limited repetition rate because of overheating. Here we report a new technique for nerve activation, namely high-speed rotation of a configuration of permanent magnets. Analytical solutions of the cable equation are derived for the oscillating electric field generated, which has amplitude proportional to the rotation speed. The prototype device built comprised a configuration of two cylindrical magnets with antiparallel magnetisations, made to rotate by interaction between the magnets' own magnetic field and three-phase currents in coils mounted on one side of the device. The electric field in a rectangular bath placed on top of the device was both numerically evaluated and measured. The ratio of the electric field gradient on frequency was approximately 1 V m(-2) Hz(-1) near the device. An exploratory series of physiological tests was conducted on the sciatic nerve and attached gastrocnemius muscle of the cane toad (Bufo marinus). Activation was readily observed of the muscle directly, at frequencies as low as 180 Hz, and of nerves bent around insulators, at frequencies as low as 230 Hz. Nerve-muscles, with the muscle elevated to avoid its direct activation, were occasionally activated, possibly in the straight section of the nerve, but more likely in the nerve where it curved up to the muscle, at radius of curvature 10 mm or more, or at the nerve end. These positive first results suggest the opportunity for a new class of small, low-cost devices for magnetic stimulation of nerves and/or muscles.

Evidence toads may modulate landing preparation without predicting impact time.

ABSTRACTWithin anurans (frogs and toads), cane toads (Bufo marinus) perform particularly controlled landings in which the forelimbs are exclusively used to decelerate and stabilize the body after impact. Here we explore how toads achieve dynamic stability across a wide range of landing conditions. Specifically, we suggest that torques during landing could be reduced by aligning forelimbs with the body's instantaneous velocity vector at impact (impact angle). To test whether toad forelimb orientation varies with landing conditions, we used high-speed video to collect forelimb and body kinematic data from six animals hopping off platforms of different heights (0, 5 and 9 cm). We found that toads do align forelimbs with the impact angle. Further, toads align forelimbs with the instantaneous velocity vector well before landing and then track its changes until touchdown. This suggests that toads may be prepared to land well before they hit the ground rather than preparing for impact at a specific moment, and that they may use a motor control strategy that allows them to perform controlled landings without the need to predict impact time.

Forelimb kinematics during hopping and landing in toads.

Coordinated landing in a variety of animals involves the re-positioning of limbs prior to impact to safely decelerate the body. However, limb kinematics strategies for landing vary considerably among species. For example, human legs are increasingly flexed before impact as drop height increases, while turkeys increasingly extend their legs before impact with increasing drop height. In anurans, landing typically involves the use of the forelimbs to decelerate the body after impact. Few detailed, quantitative descriptions of anuran forelimb kinematics during jumping exist and it is not known whether they prepare for larger landing forces by changing forelimb kinematics. In this study, we used high-speed video of 51 hops from five cane toads (Bufo marinus) to test the hypothesis that forelimb kinematics change predictably with distance. We measured excursions of the elbow (flexion/extension) and humerus (protraction/retraction and elevation/depression) throughout every hop. The results indicate that elbow and humeral excursions leading up to impact increase significantly with hop length, but do so without any change in the rate of movement. Instead, because the animal is in the air longer during longer hops, near-constant velocity movements lead to the larger excursions. These larger excursions in elbow extension result in animals hitting the ground with more extended forelimbs in longer hops, which in turn allows animals to decelerate over a greater distance.

Invasive toads don't need woolly jumpers!

![][1] Throughout the world, invasive species remain one of the most serious threats to native wildlife. Perhaps the most infamous example of such an alien invasion is that of the cane toad ( Bufo marinus ) in Australia. Released in 1935 to combat sugarcane pests, cane toads proved

Invasive toxic prey may imperil the survival of an iconic giant lizard, the Komodo dragon.

Although invasive species constitute a major threat to global biodiversity, the introduction of toxic prey into naïve predator faunas may become particularly destructive. An example of such an introduction was the deliberate release of the highly toxic cane toad (Bufo marinus) to the toad-free Australian continent in 1935. Naïve large Australian varanid lizards have recently been shown to suffer a massive increase in mortality (> 95%) when attempting to feed on this toxic amphibian. The high susceptibility of Australian varanids to toad toxin is caused by minor mutations in the sodiumpotassium- ATPase enzyme. In the present study we show that Komodo dragons (Varanus komodoensis) have similar mutations within this enzyme as observed in Australian varanids demonstrating that dragons are extremely susceptible to toad toxin. During the last decade the black-spined toad (Bufo melanostictus) has been able to invade areas close to the five toad-free islands constituting the habitat of Komodo dragons. An invasion of highly toxic black-spined toads into dragon habitats may therefore cause similar dramatic increase in dragon mortality as recorded in Australian varanids imperiling the long-term survival of this giant and iconic lizard.

Evaluation of righting reflex in cane toads (Bufo marinus) after topical application of sevoflurane jelly

To evaluate the righting reflex after topical application of a sevoflurane jelly in cane toads (Bufo marinus). 8 cane toads. Toads were 6 to 8 months of age and weighed (mean ± SD) 142.0 ± 25.2 g. Sevoflurane jelly was applied to the dorsum of each toad at a dose of 25 μL/g in trial 1 and 37.5 μL/g in trial 2. Toads were placed in dorsal recumbency every 30 seconds until loss of the righting reflex. Jelly was then removed by rinsing the toads with tap water. Toads were then left undisturbed in dorsal recumbency until return of the righting reflex. Chamber sevoflurane concentration was measured to determine vaporization. 6 of 8 toads in trial 1 and 8 of 8 toads in trial 2 lost the righting reflex. Mean ± SD time to loss of the reflex was 8.2 ± 1.3 minutes for trial 1 and 8.3 ± 0.9 minutes for trial 2; this difference was not significant. Mean ± SD time to return of the reflex was 25.6 ± 26.2 minutes for trial 1 and 84.4 ± 47.2 minutes for trial 2; this difference was significant. Chamber sevoflurane concentration did not change significantly, compared with baseline (time 0) concentration, at any time in trial 1; however, there was a significant change in chamber sevoflurane concentration from baseline (time 0) concentration in trial 2. Chamber sevoflurane concentrations were not significantly different between trial 1 and trial 2 at any time. Mean ± SD chamber sevoflurane concentration was 0.46 ± 0.2% for trial 1 and 0.57 ± 0.28% for trial 2. Sevoflurane jelly applied topically at a dose of 37.5 μL/g induced a more reliable loss of righting reflex and longer recovery time than when applied at a dose of 25 μL/g in cane toads.

Evolutionary Responses to Invasion: Cane Toad Sympatric Fish Show Enhanced Avoidance Learning

The introduced cane toad (Bufo marinus) poses a major threat to biodiversity due to its lifelong toxicity. Several terrestrial native Australian vertebrates are adapting to the cane toad’s presence and lab trials have demonstrated that repeated exposure to B. marinus can result in learnt avoidance behaviour. Here we investigated whether aversion learning is occurring in aquatic ecosystems by comparing cane toad naïve and sympatric populations of crimson spotted rainbow fish (Melanotaenia duboulayi). The first experiment indicated that fish from the sympatric population had pre-existing aversion to attacking cane toad tadpoles but also showed reduced attacks on native tadpoles. The second experiment revealed that fish from both naïve and sympatric populations learned to avoid cane toad tadpoles following repeated, direct exposure. Allopatric fish also developed a general aversion to tadpoles. The aversion learning abilities of both groups was examined using an experiment involving novel distasteful prey items. While both populations developed a general avoidance of edible pellets in the presence of distasteful pellets, only the sympatric population significantly reduced the number of attacks on the novel distasteful prey item. These results indicate that experience with toxic prey items over multiple generations can enhance avoidance leaning capabilities via natural selection.

Queensland northern quolls are not immune to cane toad toxin

Context The release of the highly toxic South American cane toad (Bufo marinus) to the toad-free Australian continent in 1935, and their subsequent rapid spread over large areas of tropical Australia, has resulted in a massive decline of predators such as yellow-spotted goannas (Varanus panoptes) and northern quolls (Dasyurus hallucatus). In spite of dramatic declines of northern quoll populations in the Northern Territory, a few populations still persist in areas of Queensland where northern quolls have co-existed with toads for several decades. Aims To determine whether the remaining quoll populations in Queensland have evolved resistance to cane toad toxins. Methods The extracellular H1–H2 domain of the α1 subunit of the sodium–potassium-ATPase gene was sequenced in four Queensland as well as four Northern Territory quolls. The transcribed sodium–potassium-ATPase enzyme from this gene is specifically targeted by toad toxins. Key results In all of the eight quolls, the sequences representing the 36 bp of the H1–H2 domain of the α1 subunit of the sodium–potassium-ATPase gene were identical. Conclusions Our results showed that Queensland quolls have not evolved an increased resistance to the toad toxins. We therefore suggest that the persistence of northern quolls in a few toad infested areas of Queensland could to be due to a combination of optimal habitat quality, and concomitant large quoll numbers, as well as an aversion to feeding on these highly toxic amphibians. Implications We suggest that a sample of northern quolls from the Queensland populations should be captured and their response, as well as that of their offspring and grand-offspring, to cane toads should be investigated to guide management of this declining species.

Prevalence of Salmonella spp. in Cane Toads (Bufo marinus) from Grenada, West Indies, and their Antimicrobial Susceptibility

Cloacal swabs and caecal contents sampled from 58 cane toads (Bufo marinus) in St George's parish, Grenada, during a 7-month period in 2011 were examined by an enrichment and selective culture method for presence of Salmonella spp. Twenty-four (41%) toads were positive for Salmonella spp. of which eight were Salmonella enterica serovar Javiana, and eight were S. enterica serovar Rubislaw. The other serovars were as follows: Montevideo, 6; Arechavaleta, 1; and serovar: IV:43:-:-, 1. The high frequency of isolation of serovar Javiana, an emerging human pathogen associated with several outbreaks in the recent years in the eastern United States, suggests a possible role for cane toads in transmission of this serovar. Although S. Rubislaw has been isolated from lizards, bats and cases of some human infections, there is no report of its carriage by cane toads, and in such high frequency. The rate of carriage of S. Montevideo, a cause for human foodborne outbreaks around the world was also over 10% in the 58 toads sampled in this study. The antimicrobial drug susceptibility tests against amoxicillin-clavulanic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, enrofloxacin, gentamicin, imipenem, nalidixic acid, streptomycin, tetracycline and trimethoprim-sulfamethoxazole showed that drug resistance is minimal and is of little concern. Antimicrobial resistance was limited to ampicillin and amoxicillin-clavulanic acid in one isolate of S. Javiana and one isolate of S. Rubislaw. This is the first report of isolation and antimicrobial susceptibilities of various Salmonella serovars not identified previously in cane toads in Grenada, West Indies.

ISOLATION BREEDS NAIVETY: ISLAND LIVING ROBS AUSTRALIAN VARANID LIZARDS OF TOAD-TOXIN IMMUNITY VIA FOUR-BASE-PAIR MUTATION

Since their introduction to the toad-free Australian continent cane toads (Bufo marinus) have caused a dramatic increase in naïve varanid mortality when these large lizards attempt to feed on this toxic amphibian. In contrast Asian-African varanids, which have coevolved with toads, are resistant to toad toxin. Toad toxins, such as Bufalin target the H1-H2 domain of the α(1) subunit of the sodium-potassium-ATPase enzyme. Sequencing of this domain revealed identical nucleotide sequences in four Asian as well as in three African varanids, and identical sequences in all 11 Australian varanids. However, compared to the Asian-African varanids, the Australian varanids showed four-base-pair substitutions, resulting in the alteration in three of the 12 amino acids representing the H1-H2 domain. The phenotypic effect of the substitutions was investigated in human embryonic kidney (HEK) 293 cells stably transfected with the Australian and the Asian-African H1-H2 domains. The transfections resulted in an approximate 3000-fold reduction in resistance to Bufalin in the Australian HEK293 cells compared to the Asian-African HEK293 cells, demonstrating the critical role of this minor mutation in providing Bufalin resistance. Our study hence presents a clear link between genotype and phenotype, a critical step in understanding the evolution of phenotypic diversity.

The invasive cane toad (Bufo marinus) in West New Britain, Papua New Guinea: observations and potential impacts on native wildlife

Since the introduction of cane toads (Bufo marinus) to East New Britain 75 years ago, they have spread rapidly across Papua New Guinea and several of its offshore islands. Their dispersal was thought to be limited by habitat constraints such as primary rainforest and altitude. However, during a scientific expedition into the Hargy Caldera and Nakanai Mountains in 2011, we made several observations of B. marinus existing within undisturbed primary rainforest habitat and at altitudes greater than 800 m above sea level. Given their propensity to reach considerable population densities and threat towards naive predators, these amphibians have the potential to have negative adverse effects on native Papua New Guinean wildlife. Future research on the potential ecological impacts of B. marinus in Papua New Guinea should be prioritized.

Dispatches

Dispatches

The weak link: do muscle properties determine locomotor performance in frogs?

Muscles power movement, yet the conceptual link between muscle performance and locomotor performance is poorly developed. Frog jumping provides an ideal system to probe the relationship between muscle capacity and locomotor performance, because a jump is a single discrete event and mechanical power output is a critical determinant of jump distance. We tested the hypothesis that interspecific variation in jump performance could be explained by variability in available muscle power. We used force plate ergometry to measure power produced during jumping in Cuban tree frogs (Osteopilus septentrionalis), leopard frogs (Rana pipiens) and cane toads (Bufo marinus). We also measured peak isotonic power output in isolated plantaris muscles for each species. As expected, jump performance varied widely. Osteopilus septentrionalis developed peak power outputs of 1047.0 ± 119.7 W kg(-1) hindlimb muscle mass, about five times that of B. marinus (198.5 ± 54.5 W kg(-1)). Values for R. pipiens were intermediate (543.9 ± 96.2 W kg(-1)). These differences in jump power were not matched by differences in available muscle power, which were 312.7 ± 28.9, 321.8 ± 48.5 and 262.8 ± 23.2 W kg(-1) muscle mass for O. septentrionalis, R. pipiens and B. marinus, respectively. The lack of correlation between available muscle power and jump power suggests that non-muscular mechanisms (e.g. elastic energy storage) can obscure the link between muscle mechanical performance and locomotor performance.